The present invention relates in general to a method of obtaining super-resolution in range for sensor systems such as electromagnetic, acoustic, electro-optics and other spectral regimes particularly where the individual sensors are limited in bandwidth. More particularly, the present invention relates to a method for producing two-dimensional (range-Doppler) images with super-resolution from a system having multiple narrow-band radars.
For both radar and sonar systems, high range resolution is a desirable property to improve the ability of the sensor in regard of target identification and discrimination. A desire to obtain resolution beyond the operating bandwidth defined by the Fourier operation has led to numerous techniques such as the Burg Algorithm which extrapolates data in the frequency domain. However, the resolution achieved by the Burg Algorithm is limited to a factor of 2 or 3 (see P. R. Wu, “A Criterion for Radar Resolution Enhancement with Burg Algorithm”, IEEE Trans., Aerospace and Electronic Systems, Vol. 31, No. 3, July, 1995), the disclosure of which is expressly incorporated herein by reference.
Other techniques have been proposed for fusing the data collected by two sensors with different operating frequencies. These techniques use estimated signals derived from two different bands to fill the empty gap so as to create a continuous ultra-wide bandwidth. The fidelity of these estimated signals is directly proportional to the inherent bandwidths of the two sensors. See “J. E. Piou, K. M. Cuomo and J. T. Mayhan, “A State-Space Technique for Ultrawide-Bandwidth Coherent Processing”, Technical Report 1054, Lincoln laboratory, Massachusetts Institute of Technology, 20 Jul. 1999 and K. M. Cuomo, U.S. Pat. No. 5,945,940, “Coherent Ultra-wideband Processing of Sparse Multi-sensor/Multi-spectral Radar Measurements” Aug. 31, 1999, the disclosures of which are expressly incorporated herein by reference. However, none of these prior art techniques has taken advantage of the interferometer principle; and therefore, full-resolution benefit implied by the frequency separation of the sensors has not been achieved.